Ebola virus causes highly lethal hemorrhagic fever in humans and non-human primates. Since the first outbreak in 1976, there have been over 20 natural human outbreaks with an average mortality rate near 70%. There are no approved agents to prevent or treat Ebola infection. Due to ease of dissemination, high lethality, and ability to cause widespread panic, the CDC defines Ebola as a Category A bioterror agent, their category of highest concern. There is great need for an effective Ebola preventative and/or treatment, to combat both natural outbreaks and potential bioterror attacks. Using an innovative mirror-image design strategy, Navigen has identified a novel D-peptide drug lead to combat Ebola. D-peptides, the mirror images of natural L-peptides, cannot be digested by proteases and, therefore, have the potential for long in vivo half-lives and reduced immunogenicity. As peptides, they can readily disrupt undruggable large protein/protein interfaces with high potency and specificity (a rare trait for small molecule drugs). Navigen's drug discovery platform employs an enantiomeric screening technology (mirror- image phage display) coupled with protein design to identify and then affinity mature D-peptides that block viruses as they attempt to enter cells. This platform technology has been successfully validated by Navigen's optimized anti-HIV drug, currently in advanced preclinical development, which binds to a highly conserved region on the HIV envelope protein and blocks entry in all major circulating HIV-1 strains. Ebola has a similarly conserved target on its surface protein, GP. Navigen's anti-Ebola drug lead binds to this conserved region and specifically inhibits pseudotyped Ebola entry into target cells with nanomolar potency. In this three-year SBIR grant, Navigen proposes to affinity mature our lead candidate through innovative phage display techniques coupled with structure-guided peptide design, demonstrate efficacy against multiple Ebola strains in tissue culture, perform preclinical pharmacokinetic (PK) studies and basic toxicology to support animal efficacy experiments, and demonstrate efficacy in gatekeeper (mouse) and gold standard (non-human primate) models of Ebola infection. Upon completion of the proposed studies, Navigen will be well positioned to execute studies that will lead to new drug approval via the Animal Rule.